Many types of modern electronic devices employ an input keypad as the user interface. The most commonly used input keypad, used primarily with phones, is shown in FIG. 1. This input keypad includes 12 keys, 10 keys for each of the numerals 0–9, a “#” key, and a “*” key. Moreover, the keys having numerals 2–9 each have various alphabetic characters associated therewith. As seen in FIG. 1, the alphabetic characters are printed on the keys in a sequence.
Using the input keypad of FIG. 1, entering numerals is straightforward. However, the entering of alphabetic characters is very cumbersome, since there are not enough keys to represent all of the letters. Various schemes have been used to allow the input keypad of FIG. 1 to enter the fill range of alphabetic characters. In most schemes, the user has to cycle through a series of keypad inputs to enter the desired letter. There is also typically a numeric/alphabetic toggle switch that switches the input keypad between numeric and alphabetic modes.
Assuming that the input keypad is in alphabetic mode, in one scheme, an alphabetic character is input by depressing the key associated with that character either 1, 2, 3 or 4 times, depending upon where the character appears in the character sequence printed on the key. Therefore, the letter A would be entered by depressing the “2” key once, the letter B may be entered by depressing the “2” key twice, and the letter C may be entered by depressing the “2” key three times. Continuing with this example, the word “HELLO” would be entered by depressing the key sequence 44, 33, 555, 555, 666. Using this method, the word “HELLO” requires thirteen keystrokes. This approach is relatively cumbersome.